Midpoint formula, point A (x 1, y 1) and point B (x2, y2). The midpoint C(x3, y3). x3=(x 1+x2)/2，y3=(y 1+y2)/2 .

At the intersection, the equations of two curves or straight lines can be simultaneous.

Distance formula from point to straight line, d = | ax0+by0+c |/√ (a? +b？ )。 Point D(x0, y0), straight line l: ax+by+c = 0.